Rules for Checking Field Values

• Validation should be considered part of the "business logic"
• Use RBS for validation, especially when used for the actual processing stage
• But the naive approach results in many rules like this one:

  rule "Check Item.code"
  when
      $item: Item( $c: code < 1 || code > 10 )
  then
      System.out.println( "Invalid code " + $c + " in " + $item );
  end
  

• Too many similar rules...